Introduction:In recent years in New Zealand there has been a growing interest in urban ecosystems because many residents enjoy having wildlife around them. This has been leading to a growing trend to plant and grow more native plants in urban gardens (Day, 15th June 1995). Over the years New Zealand’s landscape has changed a great deal since the arrival of humans in 1280-1300 AD (CITE). Since the arrival of humans, species native to New Zealand now co-exist with non-native/introduced species within urban areas. Due to the fast-acting expansion of urban landscapes and cities, the urban environment is causing a strain on local native fauna due to habitat loss. (cite)The purpose of this lab was to determine if there was a difference in of Native and Non-native bird composition in four different urban gardens around the nelson region mainly consisting of either native plants or non-native plants.
This would allow me to get a perspective to see if planting native or non-native gardens would affect the overall percentage of native or introduced birds within the urban environment thus concluding that it is beneficial or not to plant more native plants to attract more wildlife. It was decided to use birds as our model in this research project not only because this was our assignment but because they are easily surveyed and identified allowing for a better opinion on the effects of urbanisation compared to using invertebrates. (cite) I hypothesized that there would be no difference in the percentage of native and introduced birds between urban gardens having native or introduced plants. Method:This study was conducted at four different locations, two native and two non-native gardens. Isel Park, Nikau gardens, Washbourne Gardens and the bottom of Richmond hill. (see figure 1.
1) I visited each garden once for a minimum of one hour to observe each species of bird and depict whether they were native or introduced using the bird chart, gathering the total number of birds present at the time I visited. There were a few methods I kept consistent when conducting my research. The time of day I visited each garden was during mid-day, the amount of time spent at each garden, 1.5 hours (excluding the effect of rain during the Richmond hill observation). I would also spend half of my time walking through each of the gardens so I could observe different areas of the garden, which would reduce the bias of looking at one section of the garden more than another. I increased the time at each location because this allowed me to observe more visiting birds. One difficulty I encountered was that I wasn’t sure if I had already marked down a particular bird on my field data spreadsheet a couple of times so to keep the data consistent and reducing the human error I recorded the bird even if I had already observed it during the field test at all four different gardens, this allowed the data to remain fair.
Materials used:Only a few materials were needed to conduct this research project including the field data spreadsheet (figure), the printed off bird chart provided by Massey University, pens, binoculars and a means of transport to get around the different gardens.Study AreasThe region of where I studied these gardens consist of close t 14,000 residents in the Richmond area and Stoke which has in 2013 had a population of 17,163 residents (cite) All of my gardens I chase were in the heart of the two different suburbs which gave relevant data for my research project. The four gardens did vary in size which isn’t ideal. Beyond the gardens there was no bird observed. Due to the amount of time I spent at each garden, I had to visit some of the gardens on different days so I could keep the time of day I observed non-bias. (Figure 1.
1)Isel Park is a Non-Native park: Isel park was purchased by Thomas Marsden and is well known for the oldest mix of conifers and other exotic trees in NZ. (cite) On the 21st of December 2017 I visited this garden at around 11am for one and a half hours. This was the biggest garden of the four so I had to divide the garden into segments and view them separately to avoid bias observation.
On the same day 21st of Dec 2017 I managed to visit Nikau gardens, Nelsons oldest native plant nursery. (cite) for one and a half hours at 12:40pm. Although some of the native plants were only small and still growing there were plenty of fully grown native plants that provided enough of a habitat for birds to seek shelter and food as shown from my field data spreadsheet. On 29th of December 2017 I visited the bottom of Richmond hill where there is a native sanctuary. Located off of hill street, it is well amongst the popular urban area and consists of mainly native vegetation.
I only managed to visit this garden/small park for 70 minutes due to the rain. I can conclude that this would have had an effect on my results for this particular garden as rain has been proven to effect and reduce the number of bird species observed over the rainfall period. (Ratkowsky & Ratkowsky, 1979)My last urban garden I visited was Washbourn garden on the 4th of January 2018 at 12:30 for one and a half hours. This garden is centrally located in the heart of Richmond consisting of non-native plants. This was the second biggest garden of the four and similar size to isel park so I the same rules applied to split the park up.
(cite)I conducted a chi square test to analyse the data between number of native and introduced birds within a native and non-native urban garden. (x2) analysis was also used to determine if the presence of birds was random or dependant on the type of garden.Figure 1.1: Google map image of the Nelson region with locations of gardens (Google, 2001)Results:After comparing the proportion of native and non-native birds in native and non-native gardens in the nelson region using the chi-square test, I found no significant difference between the two garden types. (X2= 0.497, D.F.
=1 P<0.05) however visual observation reveals some differences.Overall the number of native birds at all four gardens was significantly lower than the introduced birds, and in general the total number of bird species found at the native garden had a difference of 10 when compared to non-native garden. (figure 2.2) As you can see from (figure 2.1) non-native gardens had a greater abundance of birds observed within the garden. My results (figure 2.2) also show there is a greater diversity of birds within the native gardens compared to the non-native garden even though the total number of birds observed was less.
Of the 102 species of birds observed roughly 50% were introduced birds. Figure 2.1: Number of birds recorded within the four different urban gardens around the Nelson region. SPECIES (N=native NN=non-native) TOTAL NO OBSERVED IN N GARDEN TOTAL NO OBSERVED IN NN GARDEN TOTAL NUMBER OBSERVED RELATIVE ABUNDANCE% Bell Bird (N) 1 1 2 1.7% Fan Tail (N) 2 5 7 6.8% Blackbird (NN) 8 7 15 14.7% Rock Pigeon (NN) 0 3 3 2.8% Silvereye (N) 4 6 10 9.
8% Song Thrush (NN) 0 7 7 6.9% House Sparrow (NN) 18 17 35 34.3% NZ Pigeon (N) 2 0 2 1.7% King Fisher (N) 1 0 1 0.8% Tui (N) 1 0 1 0.8% Yellow Hammer (NN) 3 0 3 2.8% Dunnock (NN) 2 5 7 6.
9% Grey Warbler (N) 4 0 4 3.9% Tom Tit (N) 2 0 2 1.7% Starling (NN) 3 0 3 2.8% Welcome Swallow (N) 0 5 5 4.9% TOTAL: 46 56 102 100 Figure 2.2: Species and number of birds observed in native and non-native gardens around the nelson region Discussion: After comparing the proportion of native and non-native birds within the native and non-native gardens throughout the Nelson region using a chi-square test I found no statistically significant difference between the proportions of birds of each type at the gardens because P value= <0.
05. These small deviations could have been due to chance, and therefore the data is consistent with my null hypothesis of no difference. However, many visual observations reveal that there are some differences so I cannot fully accept my null hypothesis, as my initial prediction that there would be a difference is visually shown.In this project, the findings suggest that the number or native birds within urban gardens is much lower than introduced birds. These findings disagree with my original hypothesis that there is no difference in the percentage of native and introduced birds between the urban gardens of native and introduced plants. Of the 102 birds observed between the four different gardens approximately 33% were native birds, whilst 67% were introduced birds. (Figure 2.2 or 3.
2) Others studies suggested that introduced species were most numerous in the more urbanised/introduced gardens as well as making up the greater proportion of the total birds accounted for, (cite) as well as the number of non-native birds increase in the more urbanised area. (cite) This is in accordance to my results.This study has showed that introduced bird species are affected by the configuration of plants in certain urban gardens. Native gardens in Nelson increase the diverse range of birds but attracts less introduced species present in the city. This is and isn’t in accordance to (cite) where this study in Hamilton proved that growing native gardens encourages a more diverse range of birds and attracts more of the introduced bird species within the urban area. This finding is intriguing because my result is slightly different as (cite) because although the native gardens in nelson do provide a more diverse range of birds, they don’t attract more introduced bird species like they do in Hamilton.
This result surprised me because I would have though the non-native birds would have adapted to these native plants therefore providing higher total of introduced birds. As for the more diverse range and more native birds within the native gardens I would have assumed that because the Nelson region has many more national parks such as Abel Tasman or Lake Rotoiti, it would suggest that most of the native birds in the region don’t need to seek habitat or food within urban gardens compared to Hamilton which is in agreement with (cite) stating that native birds prefer feeding within native plants/areas.There were a few limitations found in my study that would have affected my results, one of which was that the four gardens I viewed were all different sizes. It has been proven that more bird species are found in gardens with higher biomass (larger area and more plants). This wasn’t surprising because my results show that the biggest garden I observed (isel park) did indeed have the highest total number of observed in the garden. Total observed= 32 (figure 2.
1) This finding is in accordance with other studies (cite) which suggested that there would be more bird species sighted in gardens which have a larger area and higher total area because there is more available habitat and would ultimately have a larger variety of plants suiting a greater number of bird species. This would explain why there was a significant difference in the results of the total number of birds sighted at each garden.The result that the number of native birds observed in native gardens was no different to the number of native birds found in no-native gardens Total=17 each (figure 3.2) shows that within an urban environment native birds are not attracted anymore to native plants than introduced plants. This result agrees with my hypothesis of having no difference between the different gardens however is not in agreement with the study (cite) where it suggests that the more native plants in the garden, there would be a greater number of native birds within the garden. This finding is unclear and would need to be further tested but it would suggest that NZ birds are now adapting to the increased amount of introduced plants throughout the urban environment, as well as changing their preference for native plants.Figure 2.2 shows that the most common birds I observed were a non-native house sparrow.
Total of 35 and non-native blackbird total of 15 during my study. These birds were found throughout all four of my gardens which makes a very interesting observation. This result agrees with other studies (Day, 15th June 1995) showing that the house sparrow was the most common and the third most common was the blackbird. This would make sense because both bird species are both primarily ground feeders (Collins, 1999) (Jones, 2017) so the type of garden whether native or non-native wouldn’t make a huge impact on their distribution figure between the different gardens.In conclusion, the results of this research project provide some interesting insights into the difference of composition of native and introduced birds within native and non-native urban gardens around the Nelson region. Conflicting with my null hypothesis and to what I originally predicted, there was a difference in the number of native birds and introduced birds in each of the garden and almost every observed value was less than the expected values if the number of birds wasn’t affected by the garden type.
In order to confirm these findings, I would suggest that more gardens of a similar size be repeated by others. Acknowledgements:I would like to thank Ashleigh Sheehan for her assistance during field work and providing me with the necessary materials to conduct my study. Thankyou to Nikau garden/nursery for kindly allowing me access to their garden for observation.